Today, remote controlled surveillance camera systems are commonly employed as a security measure. The cameras are normally used to generate a video image of an area under surveillance that is displayed to and/or recorded for use by security personnel. In some cases, cameras are mounted to a wall or to a ceiling structure where they may be observed by people within the area under surveillance. In other cases the cameras are hidden from view as by being placed behind one-way mirror domes or the like to avoid creating an objectionable presence to an honest person and to make it difficult for or to worry potential wrongdoers by making it impossible for them to locate the cameras and to see where they are directed.
Surveillance camera systems of the types just described have had several problems and limitations associated with their use. For example, where the cameras have been located within domes that move in unison with cameras, they have not been successfully used outdoors due to adherence to, and accumulation of, snow and ice which tends to freeze the moving parts. In addition, moving domes have been virtually impossible to seal against entry into the dome of airborne particulates and insects which tend to contaminate the camera and its associated electronics. Moisture condensation within the dome can also be a problem with such systems. Even indoors, movements of the dome may be visually detected which is undesirable for discreet surveillance.
Maintenance of cameras in domes and other enclosures has been difficult and time consuming as the camera mount mechanism commonly is firmly secured within the dome and the associated control electronics, usually comprising a receiver box for receiving orientation control signals from a remote location and translating same into pan/tilt/zoom camera functions, often has been remotely located, such as above a suspended ceiling.
Surveillance cameras of the prior art also have operated in operator selectable automatic pan modes in order to provide full, continuous coverage of areas of surveillance. Generally, such cameras have been of the continuous scan type which pan or oscillate through an arc continuously at a fixed speed until stopped by an operator. Some such cameras have been incapable of full 360 degree movement and instead are mounted to actuate limit switches that border ends of arcuate paths of camera travel which reverse the direction of camera panning movement. Such continuous panning results in a constantly moving image on a video monitor which can have a hypnotizing effect on guards or other persons responsible for watching such monitors. Many activities within the camera field-of-view can thus go undetected.
Where manual controls of such cameras have been provided, the cameras have tended not to produce smooth, continuous images when operated at pan and tilt rates above about 10 degrees per second. This is because abrupt, manually controlled movements have tended to cause the cameras to wobble and vibrate, particularly where the cameras are brought to a halt as when a security guard identifies an area of interest and wishes to direct the camera in that direction for a period of time. For this reason, most camera movement control systems have been limited to pan and tilt rates of about 12 degrees or less per second. This limitation in camera movement rate can render prior art systems unsatisfactory in many situations such as when a guard is alerted to an unauthorized entry and wishes to direct the camera toward the entrance. By the time (usually several seconds) that the camera is able to pan and point in the direction of the entry, the intruder usually has moved away and thus entered undetected. A more desirable rate would correspond to an average turning rate of a human head (about 90 degrees per second) in order to detect and track fleeting events or targets.
Another problem with prior art systems that pan at fixed speeds has been their inability to track smoothly objects of varying speed or objects moving obliquely relative to the camera's optical axis. In these situations, it has been necessary to jog the cameras pan and tilt positions intermittently to point the camera just ahead of the moving object allowing the object to move through the camera's field of view prior to another such anticipatory jog.
It thus is seen that a need exists for a surveillance camera system that can be centrally located indoors and outdoors, and which is capable of continuous 360 degree panning movement for scanning a surveillance area, and which has panning and tilting rates much higher than those to which prior art systems have been limited. Such a system would further be capable of easily controllable variable pan and tilt rates for tracking variable speed or obliquely moving objects. Also, it would be desirable for the camera to be programmable to move automatically and quickly from one fixed scene to another and to be manually controllable if desired in a smooth manner at high rates without the camera jerking, wobbling and producing unsteady images during accelerations and decelerations.
It would be desirable to render the camera hidden from view without sacrifice in video quality of images produced by the camera or restricting the camera's pan and tilt movement ranges. Further, it would be desirable to provide such a camera in a compact, stationery dome type housing, with the dome having an aesthetically pleasing configuration, and with the camera and its associated control electronics being readily accessible and easily removable as a unit from its housing for maintenance. Finally, such a camera system preferably would include a programmable computer and control circuit mounted with the camera for operating the camera system in various pre-programmed modes for automatic surveillance.
It is to the provision of such a surveillance camera system, therefore, that the present invention is primarily directed.